The invention regards a camouflage material having a three-dimensional surface structure, consisting of mutually adjacent bulgements that are pointed.
Three-dimensional surface structures for camouflage purposes are previously known. An example is U.S. Pat. No. 3,069,796, which demonstrates camouflage layers which are cut in a particular way such that when stretched they assume a foliage-like structure. Another example is U.S. Pat. No. 3,836,967, which shows a radar camouflage having a multitude of similar hollow tapered pyramid-formed projections which are packed to each other and form a kind of a conducting layer.
A particular problem when camouflaging illuminated objects (including reconnaissance means in both visible and invisible light) is the difficulty of obtaining something, which resembles nature in all. A particular difficulty is that prior art camouflage surfaces appear so differently in different angles of regarding and illumination respectively. Thus, a grass surface has about the same colour and not so big difference in brightness seen against the light in comparison to light falling in at 90xc2x0 or seen in the light direction. For instance, a painted tin plate will show itself very bright seen against the light, and this independent of how good and matte a camouflage paint is used to cover the tin plate.
It is for instance shown in practice that a construction such as that shown in U.S. Pat. No. 3,836,967 is rather inappropriate for the disguise or camouflage purpose of the present invention, since its three-dimensional structure is composed from plane surfaces, which give a specular reflection, which is without importance for the use envisaged therewith, which is for radar camouflage. In visible light and e.g. the near infrared, the aspect will be far from natural.
The problem of the invention is solved according to the present invention by obtaining a three-dimensional surface that in every direction has a minimum of plane, specularly reflective surfaces. More specifically, the invention regards a camouflage material having a three-dimensional surface structure consisting of mutually adjacent pointed bulgings, characterized in having curved surfaces in essentially all sight directions.
The bulgings being stated as pointed is to be understood such that some section through them will form a sectional curve that at the top is essentially angular but can be somewhat rounded. Endings as more or less pronounced apices or edges are however preferred. If they are made as pointed, the point itself in practice will be somewhat rounded, which is also true for an edge form.
According to a preferred embodiment, the bulgings are essentially conical bulgings. With cones are to be understood according to the invention such forms which can be described by a point, a closed directrix curve which may be arbitrary or a polygon made of straight or curved lines, a circle, an ellipse, etc. and a generatrix. In the most common cases, a generatrix is a straight line, but according to the more general definition intended here, it is possible for a generatrix to be used also a curved line.
The essential is that the bulging will show up in practically all directions as curved surfaces. Simply curved surfaces will then give a specular reflection along a line. Doubly curved surfaces will give a specular reflection only in a point.
In a preferred embodiment, bulgings are used having a directrix which is circular or near circular. It is also preferred to use essentially straight lines as generatrices. According to a preferred embodiment, they will also have such angles of clearance that they easily release from a mold when made by molding.
In addition to the visual effect, it is also possible to obtain a radar camouflage effect, for example by arranging under the three-dimensional structure of a layer having radar absorption properties, which is accomplished by arranging the surface resistance as known from U.S. Pat. No. 3,733,606. Also colouring or the like with different kinds of prior art camouflage dyes is possible, as arranging favourable properties in other radiation wavelength intervals.